Treatment of polyphenyl thioethers

ABSTRACT

THE OXIDATIVE STABILITY OF POLYPHENYL THIOETHERS IS INCREASED AND THEIR CORROSIVENESS TOWARDS METALS IS DECREASED BY CONTACTING THE POLYPHENYL THIOETHERS UNDER BASIC CONDITIONS IN THE LIQUID PHASE WITH AN OXIDIZING AGENT WHICH MAINTAINS ITS OXIDATION FUNCTIONALLY UNDER BASIC CONDITIONS. FOR EXAMPLE, M-BIS(PHENYLERCAPTO) BENZENE IS CONTACTED WITH A BASIC AQUEOUS SOLUTION OF SODIUM HYPOCHLORITE AT 100*C. FOR 8 HOURS TO IMPROVE ITS OXIDATIVE STABILITY.

United States Patent 3,647,752 TREATMENT OF POLYPHENYL TI-IIOETHERS CarlW. Gieseking, St. Louis, and James D. Sullivan, Webster Groves, Mo.,assignors to Monsanto Company, St. Louis, M0. N Drawing. Filed Nov. 27,1968, Ser. No. 779,638 Int. Cl. C07c 149/30 U.S. Cl. 260-609 E 8 ClaimsABSTRACT OF THE DISCLOSURE The oxidative stability of polyphenylthioethers is increased and their corrosiveness towards metals isdecreased by contacting the polyphenyl thioethers under basic conditionsin the liquid phase with an oxidizing agent which maintains itsoxidation functionality under basic conditions. For example,m-bis(phenylmercapto) benzene is contacted with a basic aqueous solutionof sodium hypochlorite at 100 C. for 8 hours to improve its oxidativestability.

This invention relates to the treatment of certain polyphenyl thioetherswhich can also be classed as polyphenyl sulfides, which term is meant toinclude polyphenyl sulfides in which one or more, but not all of thesulfur atoms have been replaced with oxygen atoms, to improve theiroxidative stability and to decrease their corrosiveness to metals.

Because of the wide variety of applications under which functionalfluids are utilized, a concurrence of many properties, both physical andchemical, are needed in a particular fluid to provide the servicedemanded. One of the most IigOIOUs demands on fluids is made by gasturbine aircraft hydraulic systems and gas turbine engine lubricationsystems. As the speed and altitude of operation of jet powered aircraftincreases, lubrication problems also increase because of higheroperating temperatures and higher bearing pressures resulting from theincreased thrust needed to obtain higher speeds and altitudes. As theservice conditions encountered become increasingly severe, the usefullife of the functional fluid is, of course, shortened.

Polyphenyl thioethers have been proposed as compounds which can beemployed as functional fluids in many different types of application,such as hydraulic fluids, damping fluids, synthetic lubricants,particularly as gas turbine lubricants and atomic reactor coolants.

The useful life of any lubricant or hydraulic fluid can be adjudged onthe basis of many criteria such as the extent of viscosity increase, theextent of corrosion to metal surfaces in contact with the lubricant andthe extent of engine deposits.

It has now been found that the oxidative stability and thus the usefullife of polyphenyl thioethers can be greatly extended, even under thesevere conditions encountered in jet engines and other devices operatingat temperatures of the order of 500 F. and higher, by contacting suchthioethers in the liquid phase with an oxidizing agent as hereinafterdescribed. Also, by the process of this invention, the c-orrosiveness ofsuch thioethers toward certain metals is significantly reduced.

It is, therefore, an object of this invention to provide a method forincreasing the oxidation resistance of polyphenyl thioethers andcompositions thereof. Another object is to provide polyphenyl thioethersand compositions thereof which have decreased metal attack and givedecreased formation of deposits.

As used herein the term polyphenyl thioether includes a compound orphysical mixture of compounds L it L l n wherein A, A A and A are each achalkogen having an atomic number of 8 or 16, provided at least one ofA, A A and A has an atomic number of 16, X, X X X and X each areselected from the group consisting of hydrogen, alkyl, haloalkyl,halogen, arylalkyl and substituted arylalkyl, L, m and n are wholenumbers each having a value of from 0 to 8 and a is a whole numberhaving a value of from 0 to 1 provided that when a is 0, m is a wholenumber having a value of from 1 to 2. Typical examples of suchpolyphenyl thioethers are:

sum

where A and A are each selected from oxygen and sulfur;

where x and y are whole numbers from 0 to 3 and the sum of x+y is from 1to 6 and A and A are each selected from oxygen and sulfur but at leastone of A and A is sulfur.

Specific examples of polyphenyl thioethers are:

2-phenylmercapto-4'-phenoxydiphenyl sulfide2-phenylrnercapto-3'-phenoxydiphenyl sulfide2-phenoxy-3'-phenylmercaptodiphenyl sulfide3-phenoxy-4'-phenylmercaptodiphenyl sulfide2-phenoxy-4-phenylmercaptodiphenyl sulfide2-phenoxy-2'-phenylmercaptodiphenyl sulfide o-bis (phenylmercaptobenzene p-bis (phenylmerc apto benzene Phenylmercaptodiphenyl3,3'-bis(phenylmercapto)biphenyl 3-phenylmercapto-3 phenoxy) bi phenylBis (o-phenylmercaptophenyl) sulfide Bis(p-phenylmercaptophenyl) sulfideBis(m-phenylmercaptophenyl) sulfide 1,2,3-tris (phenylmercapto)benzene1-phenylmercapto-2,3'-bis (phenoxy)benzene1,3-phenylmercapto-S-phenoxybenzene 1,2,4-tris(phenylmercapto)benzene1,3,5-tris(phenylmercapto)benzene -bis (o-phenylmercaptophenylmercaptobenzene p-bis (o-phenylmercaptophenylmercapto benzene p-bis(m-phenylmercaptophenylmercapto benzene m-bis(pphenylmercaptophenylmercapto benzeneo-bis(p-phenylmercaptophenylmercapto)benzenear-bis(phenylrnercapto)-ar-(phenylmercapto)benzene 2,2-bis(phenylmercapto diphenyl ether 2,3-bis (phenylmercapto diphenyl ether2,4'-bis(phenylmercapto) diphenyl ether 4,4-bis (m-tolylmercapto)diphenyl ether 3,3'-bis(m-tolylmercapto)diphenyl ether2,4-bis(m-tolylmercapto) diphenyl ether 3,4'-bis(m-tolylmercapto)diphenyl ether 3,3-bis(p-tolylrnercapto)diphenyl ether 3 ,3 -bis(xylylmercapto diphenyl ether 4,4'-bis (xylylmercapto diphenyl ether 3,4'-bis(xylylmercapto)diphenyl ether 3,4'-bis(m-isopropylphenylmercapto)diphenyl ether3,3-bis(m-isopropylphenylmercapto)diphenyl ether 2,4-bis(m-isopropylphenylmercapto)diphenyl ether3,4--bis(p-tert-butylphenylmercapto) diphenyl ether4,4'-bis(p-tert-butylphenylmercapto diphenyl ether 3,3'-bis(p-tert-butylphenylmercapto diphenyl ether 3,3 -bis(m-di-tert-butylphenylmercapto diphenyl ether3,3'-bis(m-chlorophenylmercapto) diphenyl ether4,4'-bis(m-chlorophenylmercapto)diphenyl ether3,3-bis(m-trifluoromethylphenylmercapto)diphenyl ether 4,4-bis(m-trifluoromethylphenylmercapto) diphenyl ether3,4'-bis(rn-trifluoromethylphenylmercapto)diphenyl ether2,3'-bis(m-trifluoromethylphenylmercapto)diphenyl ether3,3'-bis(p-trifluoromethylphenylmercapto)diphenyl ether3,3-bis(o-trifluoromethylphenylmercapto)diphenyl ether3,3'-bis(m-methoxyphenylmercapto)diphenyl ether 3,4-bis(m-isopropoxyphenylmercapto diphenyl ether 3 ,4'-bis(m-perfluorobutylphenylmercapto diphenyl ether2-m-tolyloxy-2'-phenylmercaptodiphenyl sulfide2-p-tolyloxy-3'-phenylmercaptodiphenyl sulfide2-o-tolyloxy-4'-phenylmercaptodiphenyl sulfide3In-tolyloXy-3'-phenylmercaptodiphenyl sulfide3-m-tolyloxy-4-phenylmercaptodiphenyl sulfide4-m-tolyloxy-4'-phenylmercaptodiphenyl sulfide3-xylyloXy-4'-phenylmercaptodiphenyl sulfide3-Xylyloxy-3'-phenylmercaptodiphenyl sulfide3-phenoxy-3'-m-tolylmercaptodiphenyl sulfide3-phenoxy-4'-m-tolylmercaptodiphenyl sulfide2-phenoxy-3'-p-tolylmercaptodiphenyl sulfide3-phenoxy-4'-m-isopropylphenylrnercaptodiphenyl sulfide3-phenoxy-3'-m-isopropylphenylmercaptodiphenyl sulfide3-m-toloxy-3'-m-isopropylphenylmercaptodiphenyl sulfide4-m-trifluoromethylphenoxy-4'-phenylmercaptodiphenyl sulfide 43-m-trifluoromethylphenoxy-4'-phenylmercaptodiphenyl sulfide2-m-trifluoromethylphenoxy-4-phenylmercaptodiphenyl sulfide3-m-trifiuoromethylphenoxy-3'-phenyln1ercaptodiphenyl sulfide3-p-chlorophenoxy-3-phenylmercaptodiphenyl sulfide and3-m-brom0phenoxy-4-phenylmercaptodiphenyl sulfide.

Mixtures of polyphenyl thioethers can also be treated according to themethod of this invention. A typical example of a mixture of polyphenylthioethers is one which contains by weight from about 45% to about 55%rn-phenoxyphenyl-m-phenylmercaptophenyl sulfide, from about 25% to about35% bis(m-phenylmercaptophenyl) sulfide and from about 18% to about 25%bis(m-phenoxphenyl) sulfide.

Preferred polyphenyl thioethers of this invention are mixturescomprising m-bis(phenylmercapto)benzene and certain other materialswhich have properties that make them well suited for the uses disclosedabove and particularly those applications, such as jet enginelubricants, requiring thermal and oxidative stability and Wide liquidrange.

Such other materials can advantageously be employed in amounts of fromabout 20 to about 200 parts by weight per parts ofm-bis(phenylmercapt0)benzene. The other materials contemplated to beused with m-bis- (phenylmercapto)benzene to provide such preferredmixtures are as follows:

(a) The three-, four-, fiveand six-ring polyphenyl thioethers, forexample, o-bis(phenylmercapto)benzene bis (m-phenylmercaptophenyl)sulfide @TTKTO m phenylmercaptophenyl-p-phenylmercaptophenyl sulfide thetrisphenylmercaptobenzenes (VIII) such asl,2,4-trisphenylmercaptobenzene, 3,3-bis(phenylmercapto)biphenyl m-bis(p-phenylmercaptophenylmercapto) benzene,

m-bis (m-phenylmercaptophenylmercapto)benzene,

and bis[m (rn-phenylmercaptophenylmercapto)phenyl] sulfide,

(XII) E Ts-E Ist Tm-C Is-C Ts-O (b) The mixed polyphenyl oxy-thioethershaving the wherein R is a phenyl group, R is a phenylene group and Y andY are each selected from the group consisting of oxygen and sulfur,providing at least one of Y and Y is sulfur and c is a whole number from1 to 5. Examples of such mixed polyphenyl oxythioethers arem-phenylmercaptodiphenyl ether @Tlfl 3,3-bis( (phenylmercapto)dipheny1ether,

@Q'TTO 3,3-bis (phenoxy) diphenyl sulfide,

3-phenoxy-3'-phenylmercaptodiphenyl sulfide,

3-phenylmercapto-3'-phenoxydiphenyl ether,

3,4'-bis(pheny1mercapto)diphenyl ether nun-n 1-phenoxy-2,4-bis(phenylmercapto)benzene (XIX) O m-bis m-phenylmercaptophenoxy) benzene,

(c) The four-, fiveand six-ring polyphenyl ethers which can berepresented by the structure where m is 2, 3 or 4 such as bis(m-phenoxyphenyl) ether, m-phenoxyphenyl p-phenoxyphenyl ether,m-bis(m-phenoxyphenoxy) benzene, m-[(m-phenoxyphenoxy)(p-phenoxyphenoxy) ]benzene, p-[ (p-phenoxyphenoxy)(m-phenoxyphenoxy)]benzene, p bis(m-phenoxyphenoxyl)benzene,m-bis(p-phenoxyphenoxy)benzene and o-bis(-m phenoxyphenoxy)benzene andcombinations of (a) through (c). Compounds of (a) and (b) above are alsocontemplated to be employed alone or in combination with each other and(c) in the process of this invention.

The oxidizing agents which can be employed in the process of thisinvention are those oxidizing agents which will retain their oxidationfunctionality under basic conditions (as hereinafter described). Typicalexamples of such agents are sodium and calcium hypochlorite, sodiumchlorite, chlorine dioxide, hydrogen peroxide, sodium, calcium and zincperoxide, sodium, potassium and ammonium perborate, potassiumpermanganate, peroxyacetic acid, tert-butyl peroxide and benzoylperoxide.

In carrying out the process of this invention, improved polyphenylthioethers are prepared by contacting the thioethers as described abovewith an aqueous solution of the agent under basic conditions by meansknown to the art for contacting liquids with liquids, e.g., by agitatinga mixture of the thioether and the solution of oxidizing agent. In manycases, depending upon the oxidizing agent utilized, it is convenient tofirst dissolve the oxidizing agent in water, followed by the addition ofsodium or potassium hydroxide or other strong base, to bring the pH ofthe resulting solution in the range of about 9-13. The resultingsolution is then utilized to treat the thioether. The thioether can berecovered after treatment by means known to the art, for example, byfiltration or by distillation under reduced pressure.

Generally the improvements obtained by the process of this invention areunaffected by the concentration of the oxidizing agent and the time ofcontact; however, it should be realized that there are minimum values ofconcentration and time below which the process of this invention becomesimpractical. A minimum concentration of oxidizing agent of about 65% byweight of polyphenyl thioether to be treated should be used. The lengthof time of contact will vary depending upon variances in temperature andthe concentration of the contacting agent but a minimum time of aboutone-quarter hour at about 50 C. should be used. In general, times in theorder of 1 to 15 hours are sufficient for most conditions.

The temperature at which the process of this invention is carried outshould be above about 50 C. up to about C. The choice of a particulartemperature will be dictated, for example, by time available, by thefacilities available, the concentration of the contacting agent and thecharacteristics of the thioether being treated. For example, When usingthe oxidizing agent in amounts of from 2 to 3% by weight of thethioether a contact period of from about 5 to 10 hours at temperaturesin the range of about 75-100 C. provide the optimum efiiciency ofequipment and benefit to the fluid without degradation of thioether, asby forming the sulfoxide or sulfone of said thioether.

(XXII) The mechanism through which the improvements in the properties ofthe esters treated according to the method of this invention occurs isnot completely understood at this time. Particularly unexpected is theimprovement in the oxidative stability of the above-described fluidsbrought about by the process of this invention. It has been found,however, that the combined oxidation-saponification treatment issuperior to either oxidation or saponification alone.

The following non-limiting examples illustrate the process of thisinvention.

EXAMPLE 1 Into a five-liter flask fitted with a thermometer, heater,reflux condenser, agitator and a pH meter there was charged 2000 gramsof m-bis(phenylmercapto)benzene, 1000 grams of a 46% sodium hypochloritesolution, 50 grams of sodium hydroxide pellets and 950 grams of water.The resulting mixture was heated (the initial pH was about 13.3) withstirring, to 100 C. at which time the pH of the mixture was about 11.The mixture was then held at 100 C. for eight hours (with stirring) withadditional sodium hypochlorite being added whenever there was anindication (by potassium iodide paper) that hypochlorite ion was nolonger present. A total of an additional 450 grams of the sodiumhypochlorite solution was added during the eight hour hold period. Thebatch was allowed to cool overnight resulting in the formation of waterand oil layers. The layers were separated and the oil layer was washedthree times with about 2000 ml. each time of hot water. The water washeswere combined and extracted with 300 ml. of benzene. The benzeneextracts and the oil layer were combined and dehydrated (to 130 C.)under vacuum and the residue distilled (to 250 C.) to provide about 1900grams of treated m-bis(phenylmercapto)benzene.

EXAMPLE 2 Generally following the procedure of Example 1 except omittingthe sodium hydroxide, 2000 grams of m-bis- (phenylmercapto)benzene and1000 grams of 4-6% sodium hypochlorite were heated at about 90 C. forabout eight hours with the addition of 800 ml. of the hypochloritesolution during the heating period so as to maintain a positivepotassium iodide test, washed and distilled.

EXAMPLE 3 Generally following the procedure of Example 1 except omittingthe sodium hypochlorite, 1548 grams of m-bis- (phenylmercapto)benzenewere heated with 83 grams of 98% sodium hydroxide and 1548 grams ofwater at 100 C. for about eight hours, washed and distilled.

The treated fluid from the above examples was tested in a recognizedbench test to determine its oxidative stability and corrosiveness tometal. The results of these tests are reported in Table I.

The data reported in Table I was obtained by employing the proceduredescribed in Federal Test Specification 791, Method 5308, except thatthe fluid tested was heated to a temperature of 500 EF. for a period of48 hours instead of 250 IF. for 168 hours as specified in said method,in the presence of certain metals and air. The viscosity increase of thefluid is determined as well as information as to the corrosiveness ofthe test fluid to metals. In order to demonstrate the effectiveness ofthe process of this invention in improving the oxidative stability andreduced corrosiveness of the fluids, samples of the fluid treated asdescribed above and on an untreated sample of the same fluid (control)were tested. The metal specimens used were steel, copper, silver,titanium, magnesium alloy and aluminum alloy. However, only the resultsupon copper and silver are reported since the untreated fluid tested hadessentially no effect TABLE I Percent Metal attack. Decrease in metalviscosity rug/cm. attack. percent increase at Ex. N0. F. Cu Ag Cu AgControl 8.5 3. 3 1.9 3.2 1.7 -0.9 48.5 52.7 -3.0 1.7 9.1 10.7 Control18. 9 -4. 1 3. 3 14. 5 3. 5 2. 2 14. 3 33. 4

From the data in Table I above the reduction in viscosity increaseindicates the increased oxidative stability of polyphenyl thioethers andthe reduction in corrosiveness to copper and silver brought about bytreating such thioethers according to the process of this invention.Thus, the useful life of the polyphenyl thioethers is improved accordingto the process of this invention.

While this invention has been described with respect to various specificexamples of embodiments, it is understood that the invention is notlimited thereto and that it can be variously practiced within the scopeof the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for improving the oxidative stability and to decrease thecorrosiveness to metals of polyphenyl thioethers which comprisescontacting at a temperature of from about 50 C. to about C., in theliquid phase and under basic conditions, a polyphenyl thioether with anaqueous solution of an oxidizing agent which maintains its oxidativefunction under basic conditions, for a period of time sufficient toimprove the oxidative stability and to decrease the corrosivity tometals of the polyphenyl thioether.

2. The process of claim 1 where the contacting is at a pH of about 9'.

3. The process of claim 1 where the oxidizing agent is an alkali metalhypochlorite.

4. The process of claim 3 where the oxidizing agent is sodiumhypochlorite.

5. The process of claim 4 wherein the polyphenyl thioether ism-bis(phenylmercapto)benzene.

6. The process of claim 1 wherein the polyphenyl thioether isrepresented by the formula:

where m is a whole number from 0 to 6.

7. The process of claim 6 wherein the polyphenyl thio ethers ism-bis(phenylmercapto)benzene.

9 8. The process of claim 1 wherein the polyphenyl References Citedthioether is a mixture comprising, by Weight, from about UNITED STATESPATENTS 42% to about 99% m-bis(phenylmercapto)benzene and 3 098,1036/1963 Reifschneider from about 17% to about 58% of a mixturecomprising,

by weight, from about 20% to about bis(m-phenyl- 5 ALEX MAZEL, PrimaryExaminer mercaptophenyl) sulfide, from about to about PHILLIPS,Assistant Examiner 3-phenoxy 3-phenylmercaptodipheny1 sulfide and fromabout 20% to about 30% bis(m-phenoxyphenyl) sulfide and the oxidizingagent is sodium hypochlorite. 10 252--45, 48.2, 48.4; 260-609 F

